1. Field of the Invention
The invention relates generally to communication in information processing systems and more specifically to notifying parts of systems that changes in other parts of the system have occurred.
2. Description of the Related Art
A recent advance in the design of computers involves hot-pluggability, the ability to connect a device to a computer bus while the computer is operating, and have that device communicate properly with the computer. In the past, computers could only be reliably connected to devices when power was not supplied. Now, busses have been designed which function properly when devices are connected or powered-up after the bus has power.
Unfortunately, solving the electrical problems associated with hot-pluggability does not guarantee that the device will communicate with the computer. The computer must be made aware that the device has been connected, and must be made aware of how that device communicates. This problem is typically solved either by having the computer poll the newly connected device for this information, or by having the newly connected device announce its presence.
Even this does not solve all problems involved with connecting a device to a computer after the computer starts operating. Clients, such as application programs and other routines may be established on the computer, as background processes, foreground processes, or as quiescent routines awaiting activation. If these clients have already determined which devices are connected before the newly connected device is connected to the bus, the clients may not be able to take advantage of the presence of the newly connected device. Therefore, what is needed is a method or apparatus for notifying clients of the presence of the newly connected device. Furthermore, not all application programs or routines may want to know of specific devices being connected, so what is also needed is a method or apparatus for selectively notifying clients of the presence of newly connected devices.